There are conventionally known writing instruments such as ball-point pens and felt-tip pens as liquid applicators. Commercially available ball-point pens each generally incorporate a ball for application made of a hard material such as tungsten cemented carbide, stainless steel, and ceramic in a tip unit of a pen tip.
On the other hand, liquid applicators of a ball-point pen type incorporating a ball made of an elastic body such as rubber in a tip unit of a pen tip have been proposed as disclosed in Patent Documents 1 to 3.